Charles Dayton, VP for market analytics for Doyle Trading Consultants, said he expects US coal exports to peak this year at about 120 million st.

While US producers may face fewer regulatory and capacity challenges at home, Dayton said in his presentation December 4, revised economic forecasts from the International Monetary Fund point to slowdowns in vital thermal markets such as India and Turkey. He said he also sees "storm clouds" for U.S. producers in recent economic activity in Germany and Japan.

The threat of escalating trade tensions could add further strain to U.S. suppliers with an eye on the international market, said Lucas Pipes, senior VP and senior analyst for B. Riley FBR.

Pipes said the perception that the standoff with China had evolved from an opportunity to a market risk was worrisome for U.S. coal and metals producers, who could face "tit-for-tat retaliatory tariffs and duties" as well as other unintended consequences if current talks fail to address the concerns of both sides.

In the case of a broader global economic slowdown, Pipes said, domestic metallurgical producers would be significantly exposed to a decline in demand, as nearly 75% of their product went to the export market in 2017.

Further, continued steel tariffs on U.S. imports could add to production costs for underground miners. According to Pipes, steel structures account for about 10% to 15% of their costs.

Janet Gellici, CEO of the National Coal Council, said regulatory uncertainty about the staying power of the Trump administration's efforts to assist the coal industry could also slow needed investment in export efforts for US producers.

In a report presented to U.S. Department of Energy Secretary Rick Perry in late October, the NCC outlined the main challenges for U.S. exports, including structural and regulatory obstacles, the lack of Western port capacity and competition for European and Asian customers.

Gellici said the NCC offered a series of policy suggestions, including using federal facilities to expand port capacity on the West Coast and encouraging international financial institutions to support coal-related projects in other countries, but it is unclear whether they would be adopted in time to counter an expected downturn in demand for U.S. coal abroad.